Skip to main content

AWS - Block Storage

· 3 min read

Amazon Elastic Block Store (EBS) provides persistent storage for Amazon EC2 instances.

Imagine a restaurant where each chef (EC2 instance) has their own personal fridge (EBS volume) for storing ingredients.

Key Characteristics​

  • Local Fridge in the Same Station (Availability Zone)

    • When you bring in a fridge (create an EBS volume), it stays within the same kitchen station (Availability Zone or AZ).
    • To prevent losing ingredients in case the fridge's hardware fails, it automatically has redundant components (replication) within that station.

  • Attach to One Chef at a Time (Single Instance Attachment)

    • A fridge belongs to a specific chef (EC2 instance). Even if another chef is in the same kitchen station (AZ), they cannot access the fridge unless the first chef detaches from it.
    • The fridge must stay within the same AZ where it was created.

  • Multi-Attach: One Fridge Shared by Multiple Chefs

    • Certain premium fridges (Provisioned IOPS SSD, io1 volumes) in a Nitro-based kitchen allow multiple chefs (EC2 instances) to access the same fridge simultaneously.
    • Other fridge types don't allow multiple chefs to open them at once.

  • Independent from the Chef's Employment

    • The fridge isn't discarded if the chef leaves (instance terminates). You can choose not to remove it automatically.
    • It can remain off-instance and be reassigned if needed.

  • Live "Fridge" Upgrades (Volume Modification on the Fly)

    • If you need a bigger fridge (increase volume size) or a different model (change volume type), you can upgrade on the fly without disrupting the chef's work.

  • Lock and Key Security (Encryption)

    • (Optional) Every fridge come with a secure lock (encryption) using AES-256 encryption.
    • Ensures only authorized personnel can open or move the fridge.

  • High Reliability (99.999% SLA)

    • The fridge is incredibly reliable, designed to operate for nearly its entire service life (99.999% SLA).

Common Misunderstandings​

  1. "Fridges Are Replicated to Another Restaurant Region"

    • Incorrect. Fridges are only replicated within the same kitchen station (AZ). There's no automatic copy to another Region.

  2. "Any Chef in Any Station Can Use the Same Fridge"

    • Incorrect. A fridge created in one station (AZ) cannot be simply wheeled to another station. You can only attach it to chefs in the same Availability Zone. That too you need to detach from existing chef, before attaching to another chef.

  3. "Snapshots Go to Amazon RDS"

    • Almost but not quite. When you take a snapshot (backup) of a fridge, that snapshot is stored in Amazon S3, not Amazon RDS.
    • Think of S3 as a big central warehouse where you can keep a backup of your fridge's contents for safekeeping.